Geological Society, London, Memoirs The variety and distribution of submarine glacial landforms and implications for ice-sheet reconstruction by J. A. Dowdeswell, M. Canals, M. Jakobsson, B. J. Todd, E. K. Dowdeswell, and K. A. Hogan Geological Society, London, Memoirs Volume 46(1):519-552 November 30, 2016 © 2016 The Author(s). Published by The Geological Society of London

The global distribution of glaciers and ice sheets and the glacier-influenced, or glacimarine, environment. The global distribution of glaciers and ice sheets and the glacier-influenced, or glacimarine, environment. The approximate modern (yellow dotted line) and Quaternary full-glacial (yellow dashed line) limits of ice-rafting and ice-keel ploughing of the seafloor are shown (modified from Anderson 1983). GEBCO World Map: Gall projection. Numbered yellow dots refer to the locations of subsequent figures. J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

Submarine examples of streamlined subglacial landforms and those located at the lateral margins of ice streams. Submarine examples of streamlined subglacial landforms and those located at the lateral margins of ice streams. (a) Streamlined Rogen moraines with superimposed transverse-to-flow small retreat ridges in a Svalbard fjord (modified from Dowdeswell & Ottesen 2016a). (b) Part of a drumlin field in the Gulf of Bothnia (modified from Jakobsson et al. 2016a). (c) MSGLs on the floor of Marguerite Trough, Antarctic Peninsula (modified from Ó Cofaigh et al. 2016a). (d) Crag-and-tails on the Amundsen Sea shelf, Antarctica (modified from Nitsche et al. 2016a). (e) String of aligned glacitectonic rafts in the Barents Sea (modified from Rüther et al. 2016). (f) Lateral shear-margin moraine at the edge of a Norwegian cross-shelf trough (modified from Batchelor & Dowdeswell 2016). Several artefacts are labelled A. Black arrows show the direction of past ice flow. J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

Submarine examples of non-streamlined subglacial landforms. Submarine examples of non-streamlined subglacial landforms. (a) Hill–hole pair on Trænabanken, west of Norway (modified from Dowdeswell et al. 2016h). A is an example of an artefact. (b) Rhombohedral pattern of crevasse-fill ridges in a Svalbard fjord (modified from Dowdeswell & Ottesen 2016a). J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

Submarine examples of landforms produced by subglacial meltwater. Submarine examples of landforms produced by subglacial meltwater. (a) An esker, with small transverse ridges superimposed on it, in Svalbard fjord (modified from Dowdeswell & Ottesen 2016a). (b) Tunnel valley in the North Sea from Olex data (modified from Stewart 2016). J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

Large subglacially eroded landforms. Large subglacially eroded landforms. (a) The 5 km-wide and steep-walled Nordvestfjorden, inner Scoresby Sund, East Greenland (photo: J.A. Dowdeswell). (b) The Laurentian Channel: a cross-shelf trough on the Scotian Shelf, Atlantic Canada (modified from Todd 2016a). J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

Submarine examples of ice-marginal landforms. Submarine examples of ice-marginal landforms. (a) The huge Skjoldryggen terminal moraines off mid-Norway (modified from Dowdeswell et al. 2016g). Some iceberg ploughmarks are visible on the ridge crest and beyond. (b) Transverse-to-flow De Geer retreat moraines on the Scotian Shelf, Atlantic Canada (modified from Todd 2016b). (c) Hummocky terrain and a shelf-edge moraine ridge off mid-Norway (modified from Dowdeswell et al. 2016h). (d) A grounding-zone wedge (GZW) on the floor of Pine Island Bay, West Antarctica (modified from Anderson & Jakobsson 2016). The GZW overrides mega-scale glacial lineations (MSGLs) and has ploughmarks on its surface. J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

Glacial landforms on high-latitude continental slopes. Glacial landforms on high-latitude continental slopes. (a) The Bear Island TMF, Barents Sea margin, with glacigenic debris-flows on its surface (modified from Laberg & Dowdeswell 2016). (b) Glacigenic debris-flows on the Bear Island Fan imaged from GLORIA 6 kHz system (modified from Laberg & Dowdeswell 2016). (c) Buried glacigenic debris-flows in the North Sea Fan imaged on a palaeoshelf from 3D seismic-reflection data (modified from Ottesen et al. 2014). (d) Submarine channels on the Labrador slope, Atlantic Canada, offshore of a cross-shelf trough (modified from Dowdeswell et al. 2016d). A, artefacts. J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

(a) Ice-proximal fan and tidewater glacier in eastern Baffin Island, Canadian Arctic (modified from E. Dowdeswell et al. 2016a). (a) Ice-proximal fan and tidewater glacier in eastern Baffin Island, Canadian Arctic (modified from E. Dowdeswell et al. 2016a). (b) Smooth basin-fill and buried moraine ridges in Royal Bay, South Georgia (modified from Graham & Hodgson 2016). Example of an artefact is labelled A. (c) Fjord delta fed from a fluvial system in Valldal, Norway (modified from Eilertsen et al. 2016). J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

Ice-keel ploughmarks in the glacimarine record. Ice-keel ploughmarks in the glacimarine record. (a) Large sub-parallel iceberg ploughmarks and push-ridges in Pine Island Bay, West Antarctica (modified from Jakobsson & Anderson 2016). (b) Chaotic iceberg ploughmarks off Austfonna, northern Barents Sea, eastern Svalbard (courtesy of the Norwegian Hydrographic Service, permission no. 14G/754). (c) Iceberg ploughmarks buried about 700 m deep in the central North Sea and imaged from 3D seismic-reflection data (modified from Dowdeswell & Ottesen 2016b). A marks a processing artefact. (d) Enigmatic MSGL-like lineations on the Lomonosov Ridge, Arctic Ocean, probably formed by ice-shelf grounding (modified from Jakobsson et al. 2010). J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

Other features on the seafloor of high-latitude fjords, shelves and slopes. Other features on the seafloor of high-latitude fjords, shelves and slopes. (a) Sediment slides off the fjord walls of Smeerenburgfjorden, NW Svalbard (modified from Dowdeswell et al. 2016e). (b) The upper part of the huge Hinlopen Slide with the outer shelf north of Svalbard in red (modified from Hogan et al. 2013). DR are detached sediment ridges. (c) Debris-flow lobes on the distal slope of a terminal-moraine ridge, Borebukta, Spitsbergen (modified from Dowdeswell et al. 2016f). (d) Andøya Canyon, Barents Sea margin (modified from Laberg et al. 2016). (e) Gullies on the slope offshore of the Weddell Sea shelf edge, Antarctica (modified from Gales et al. 2016). (f) The confluence of two turbidite channels on the abyssal seafloor of the Greenland Basin (modified from García et al. 2016). Features labelled A in panels (e) and (f) are artefacts. J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

(a) Turbidite channels on the floor of Nordvestfjorden, inner Scoresby Sund, East Greenland (modified from Dowdeswell et al. 2016a). (a) Turbidite channels on the floor of Nordvestfjorden, inner Scoresby Sund, East Greenland (modified from Dowdeswell et al. 2016a). (b) Sediment waves on a shallow moraine ridge, Raudfjorden, NW Svalbard (modified from Dowdeswell & Ottesen 2016c). Parallel stripes, which are processing artefacts, trend roughly north–south in the image. J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

Disturbance of seafloor sediments on high-latitude shelves. Disturbance of seafloor sediments on high-latitude shelves. (a) Pockmarks in the SW Barents Sea (modified from Chand et al. 2016). (b) Trawl marks and possible whale-feeding marks in the Barents Sea (modified from Thorsnes et al. 2016). (c) Pipeline (1.5 m wide) crossing an otherwise flat area of the Baltic Sea floor (courtesy of UK Seafloor Mapping Ltd.). J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

Graph showing the estimated range in volume of a number of submarine glacial landforms and the approximate timescales over which they build up. Graph showing the estimated range in volume of a number of submarine glacial landforms and the approximate timescales over which they build up. Note the order-of-magnitude scales. J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

(a) Ice-flow directions (indicated by arrows and based on the orientation of streamlined subglacial landforms in the coloured multibeam data) and the estimated size of the Quaternary basin (outlined in white and about 220 000 km2 in area) draining full-glacial ice into the Belgica Trough area of the Bellingshausen Sea (modified from Ó Cofaigh et al. 2005b). (a) Ice-flow directions (indicated by arrows and based on the orientation of streamlined subglacial landforms in the coloured multibeam data) and the estimated size of the Quaternary basin (outlined in white and about 220 000 km2 in area) draining full-glacial ice into the Belgica Trough area of the Bellingshausen Sea (modified from Ó Cofaigh et al. 2005b). The modern ice sheet is shaded light grey and floating ice shelves are dark grey. (b) Multibeam data from the inner Bellingshausen Sea and Ronne Entrance showing the orientation of streamlined subglacial landforms (modified from Ó Cofaigh et al. 2005b). Small black arrows point to crudely streamlined bedforms and thin dashed lines are streamlined glacial lineations. Larger dark grey, red and brown arrows indicate former ice-flow directions and correspond to arrows of the same colour in (a). J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

(a) Multibeam-bathymetric image of Malangsdjupet cross-shelf trough on the Norwegian shelf, showing submarine landforms in the trough and on the adjacent shallower banks (image provided by the MAREANO project). (a) Multibeam-bathymetric image of Malangsdjupet cross-shelf trough on the Norwegian shelf, showing submarine landforms in the trough and on the adjacent shallower banks (image provided by the MAREANO project). (b) Location map (red box; map from IBCAO v. 3.0). (c) Distribution of major cross-shelf troughs (red) and TMFs (orange) in the High Arctic (modified from Batchelor & Dowdeswell 2014). BB is Baffin Bay, QEI are Queen Elizabeth Islands. J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

The complexity of past ice flow shown by cross-cutting flow sets of MSGLs and other glacial landforms mapped from multibeam data in the McMurdo Sound area of the Ross Sea, Antarctica (modified from Greenwood et al. 2012). The complexity of past ice flow shown by cross-cutting flow sets of MSGLs and other glacial landforms mapped from multibeam data in the McMurdo Sound area of the Ross Sea, Antarctica (modified from Greenwood et al. 2012). Sets of flow features (MSGLs parallel to ice flow and moraines transverse to flow) are indicated by grey boxes which are labelled from 1 (oldest in relative age) to 7 (youngest). Grey arrows indicate the ice-flow direction of each flow-set of MSGLs. Red arrows indicate ice-retreat direction from moraine-ridge orientations. Cross-cutting relationships are shown in white circles. J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

The assemblages of submarine glacial landforms that characterize (a) ice stream and (b) inter-ice stream settings on high-latitude continental shelves (modified from Ottesen & Dowdeswell 2009). The assemblages of submarine glacial landforms that characterize (a) ice stream and (b) inter-ice stream settings on high-latitude continental shelves (modified from Ottesen & Dowdeswell 2009). LIA, Little Ice Age; MSGL, mega-scale glacial lineations. J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

Schematic diagram of the transition in submarine glacial landforms that takes place as ice flows from an interior ice-sheet drainage basin into a cross-shelf trough (modified from Wellner et al. 2001, 2006). Schematic diagram of the transition in submarine glacial landforms that takes place as ice flows from an interior ice-sheet drainage basin into a cross-shelf trough (modified from Wellner et al. 2001, 2006). Bedrock landforms are replaced by progressively more elongate streamlined sedimentary landforms as fast ice-stream flow takes place over a deformable bed. J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

The environmental continuum of glacimarine environments from the mildest to the coldest locations where ice reaches the sea. The environmental continuum of glacimarine environments from the mildest to the coldest locations where ice reaches the sea. (a) Modern, Quaternary interglacial conditions. (b) Quaternary full-glacial conditions. (c) Some of the characteristic sediments and landforms associated with milder and colder glacimarine environments. J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London

Schematic diagram of the effects of changing surface-meltwater abundance on glacial landform development in marine ice-marginal settings. Schematic diagram of the effects of changing surface-meltwater abundance on glacial landform development in marine ice-marginal settings. (a) Mild glacimarine setting with abundant surface meltwater. Ice-proximal fans, morainal banks and subglacially formed tunnel valleys and eskers are present (based in part on Powell 1990; Dowdeswell et al. 2015). Note the grounded tidewater ice cliff with no floating ice shelf beyond due to relatively mild ocean temperature. (b) An intermediate glacimarine setting, where surface meltwater is present during regional deglaciation, exemplified by Kveitola, western Barents Sea (modified from Bjarnadóttir et al. 2013). GZW, grounding-zone wedge. (c) GZW formed in a colder high-latitude glacimarine setting where only basal meltwater is available (based in part on McMullen et al. 2006; Dowdeswell & Fugelli 2012). (d) GZW in a high-polar glacimarine setting with no evidence of channels, where basal meltwater flows only in deforming till. (e) Large ice-proximal fan produced at the southern margins of a Quaternary ice sheet as a result of catastrophic drainage of an ice-dammed or subglacial lake (based in part of Winsemann et al. 2009). Note that the schematic diagrams are not drawn to the same scale. J. A. Dowdeswell et al. Geological Society, London, Memoirs 2016;46:519-552 © 2016 The Author(s). Published by The Geological Society of London